Dump trucks or so-called large dump trucks are predominantly used in coal mining operations or ore mining operations for the transport of the mined coal, minerals and ores. These bulk material dumpers are manufactured in sizes of more than 90 metric tons (t) up to several 100 t in weight and payload so that they have very large dimensions overall.
A diesel electric drive is used as the traction drive, wherein the mechanical energy generated by a diesel engine is converted with the aid of a generator into electrical energy for the supply of the electric traction drives. The reason for this procedure is that diesel engines, like all internal combustion engines, can only be operated with ideal efficiency in a very restricted speed range and cannot be started under load. The AC motors for the driving axle which are used can also produce the desired torque in the lower speed range for starting. The internal combustion engine used can be operated continuously in the ideal speed range.
Previously, all auxiliary consumers of the vehicle have been electrically driven; thus, for example, all components for the operation of a cooling air-based cooling system of the work machine. The energy supply of the motorized components of the cooling system has previously been provided by the generator of the diesel electric drive. It is a disadvantage of this procedure that different voltage circuits have to be produced for the different auxiliary consumers. For this purpose, at least one further power electronics module is required in addition to the power electronics for the control of the electrical traction drive, the further power electronics providing a suitable DC voltage circuit for the feeding of any auxiliary consumers such as blower motors, etc.
It is the object of the present disclosure to show an innovative concept for the energy supply of the auxiliary consumers of a mobile work machine of the category.
This object is achieved by a mobile work machine having a diesel electric traction drive and a cooling system for the cooling of any system components. The required components for the provision of the cooling system will be termed auxiliary consumers in the following.
In accordance with the present disclosure, at least the auxiliary consumers of the cooling system, i.e., at least two radiator fans and/or cooling blowers of the cooling system, which are configured as radial fans, are hydraulically driven. The radiator fans or cooling blowers accordingly each comprise hydraulic motors which are associated with them and which can be supplied by a hydraulic circuit having the required pressure. In accordance with the present disclosure, the radiator fans and/or cooler blowers are now no longer electrically supplied by the provided energy of the generator, but are instead hydraulically driven.
The radiator fans serve the sucking in of the cooling air, while the cooling fans serve to control the cooling air flow within the flow passages.
The present disclosure results in a simplification of the power electronics since previously necessary components of the power electronics for providing a separate DC voltage circuit for the supply of the electrical fan motors can be dispensed with. The manufacture and maintenance of the power electronics is simplified and less expensive. The hydraulic drive of the fan motors and/or blower motors is in contrast characterized by a higher stability and reliability, which proves to be a great advantage particularly with work machines in the form of dump trucks due to the extreme environmental conditions at the deployment site. In addition, an operation of the fan motors and/or blower motors can be ensured practically independently of the operating conditions of the internal combustion engine.
In an example embodiment of the present disclosure, the generated electricity of the diesel electric traction drive serves only the feed of the one or more traction drive motors. The supply of all further auxiliary consumers, in particular each and every consumer of the cooling system, is implemented by the integration of one or more hydraulic circuits.
The required hydraulic energy for feeding the hydraulic motors for the radiator fans or for the cooling blowers is provided by one or more hydraulic pumps. The drive of the hydraulic pumps advantageously takes place via at least one transfer case which can be flanged either directly to the internal combustion engine, for example via a belt connection, or alternately on the outgoing engine shaft at the internal combustion engine or at the incoming or outgoing side at the generator. It is important in this embodiment that the internal combustion engine drives the generator directly, in particular by a shaft passing through the transfer case, so that any transmission losses of the drive train between the internal combustion engine and the generator are very largely avoided. A defined portion of the engine torque is branched off via the transfer case to drive the hydraulic pumps. Alternatively, one or more hydraulic pumps can also be connected directly to the internal combustion engine via a belt connection.
In an example embodiment of the present disclosure, the utilized hydraulic drive of the respectively associated radiator fan or cooling fan is operable at a fixed or variable speed. The setting of the required speed can in particular be set independently of the operating point of the internal combustion engine or of the generator.
The respectively used radiator fan is a radial fan which is driven by at least one hydraulic motor.
In an example embodiment of the present disclosure, one or more air guidance passages run in the direction of the one or more electric drives, i.e., in the direction of the electric motors of the driven vehicle axle, in particular, the rear axle, and/or in the direction of one or more components of the power electronics of the diesel electric drive, in particular frequency inverters, and/or to the generator of the diesel electric drive itself. Sufficient cooling air can be conveyed in the direction of the components to be cooled by means of one or more cooling fans within the air guidance passages so that a sufficient cooling is achieved.
The radiator fans or the radial fans are in particular arranged, viewed in the direction of travel, behind an upper deck of the work machine and/or above or on the generator of the diesel electric drive.
Further advantages and properties of the present disclosure will be explained in more detail with reference to an embodiment shown in the drawings.